This invention relates to medical apparatus and methods in general, and more particularly to apparatus and methods for reconstructing ligaments.
Ligaments are tough bands of tissue which serve to connect the articular extremities of bones, or to support or retain organs in place within the body. Ligaments are typically composed of coarse bundles of dense white fibrous tissue which are disposed in a parallel or closely interlaced manner, with the fibrous tissue being pliant and flexible, but not significantly extensible.
In many cases, ligaments are torn or ruptured as a result of accidents. As a result, various procedures have been developed to repair or replace such damaged ligaments.
For example, in the human knee, the anterior and posterior cruciate ligaments (i.e., the ACL and PCL) extend between the top end of the tibia and the bottom end of the femur. The ACL and PCL cooperate, together with other ligaments and soft tissue, to provide both static and dynamic stability to the knee. Often, the anterior cruciate ligament (i.e., the ACL) is ruptured or torn as a result of, for example, a sports-related injury. Consequently, various surgical procedures have been developed for reconstructing the ACL so as to restore normal function to the knee.
In many instances, the ACL may be reconstructed by replacing the ruptured ACL with a graft ligament. More particularly, with such procedures, bone tunnels are typically formed in the top end of the tibia and the bottom end of the femur, with one end of the graft ligament being positioned in the femoral tunnel and the other end of the graft ligament being positioned in the tibial tunnel. The two ends of the graft ligament are anchored in place in various ways known in the art so that the graft ligament extends between the femur and the tibia in substantially the same way, and with substantially the same function, as the original ACL. This graft ligament then cooperates with the surrounding anatomical structures so as to restore normal function to the knee.
In some circumstances the graft ligament may be a ligament or tendon which is harvested from elsewhere in the patient; in other circumstances the graft ligament may be a synthetic device. For the purposes of the present invention, all of the foregoing can be collectively referred to as a xe2x80x9cgraft ligamentxe2x80x9d, xe2x80x9cgraft materialxe2x80x9d or xe2x80x9cgraft member.xe2x80x9d
As noted above, the graft ligament may be anchored in place in various ways. See, for example, U.S. Pat. No. 4,828,562, issued May 9, 1989 to Robert V. Kenna; U.S. Pat. No. 4,744,793, issued May 17, 1988 to Jack E. Parr et al.; U.S. Pat. No. 4,755,183, issued Jul. 5, 1988 to Robert V. Kenna; U.S. Pat. No. 4,927,421, issued May 22, 1990 to E. Marlowe Goble et al.; U.S. Pat. No. 4,950,270, issued Aug. 21, 1990 to Jerald A. Bowman et al.; U.S. Pat. No. 5,062,843, issued Nov. 5, 1991 to Thomas H. Mahony, III; U.S. Pat. No. 5,147,362, issued Sep. 15, 1992 to E. Marlowe Goble; U.S. Pat. No. 5,211,647, issued May 18, 1993 to Reinhold Schmieding; U.S. Pat. No. 5,151,104, issued Sep. 29, 1992 to Robert V. Kenna; U.S. Pat. No. 4,784,126, issued Nov. 15, 1988 to Donald H. Hourahane; U.S. Pat. No. 4,590,928, issued May 27, 1986 to Michael S. Hunt et al.; and French Patent Publication No. 2,590,792, filed Dec. 4, 1985 by Francis Henri Breard.
Despite the above-identified advances in the art, there remains a need for a graft ligament anchor which is simple, easy to install, and inexpensive to manufacture, while providing secure, trouble-free anchoring of the graft ligament, typically in the knee joint of a mammal.
Accordingly, one object of the present invention is to provide an improved graft ligament anchor which is relatively simple in construction and therefore inexpensive to manufacture, relatively easy to handle and install, and reliable and safe in operation.
Another object of the present invention is to provide an improved method for attaching a graft ligament to a bone.
These and other objects of the present invention are addressed by the provision and use of a novel graft ligament anchor comprising graft ligament engagement means for disposition in an opening in a bone, such that a wall of the graft ligament engagement means resides adjacent to at least one graft ligament disposed in the opening, and locking means for disposition in the opening in the bone and at least partially engageable with the graft ligament engagement means. The elements of the graft ligament anchor are adapted such that movement of the locking means in the opening in the bone causes at least a part of the locking means to engage the graft ligament engagement means so as to urge the graft ligament engagement means, and hence the portion of the graft ligament disposed adjacent thereto, toward a wall of the opening in the bone, whereby to secure the graft ligament to the wall of the opening.
In use, an opening is made in the bone, and the graft ligament and the graft ligament engagement means are inserted into the opening, with a portion of the graft ligament being disposed alongside a wall of the graft ligament engagement means. In accordance with the present invention, the locking means are also positioned in the opening in the bone, alongside the graft ligament engagement means, with the locking means being separated from the graft ligament by a portion of the graft ligament engagement means. The method further includes moving the locking means in the opening in the bone so as to cause at least a portion thereof to urge the graft ligament engagement means, and hence the portion of the graft ligament disposed adjacent thereto, toward a wall of the opening, whereby to secure the graft ligament to the wall of the opening.
In one aspect of the invention, a graft fixation device for fixing a graft member within a bone tunnel includes a radially expandable sheath having a side wall with at least one structurally weakened fracture region extending longitudinally along a length of the sheath in the side wall. The radially expandable sheath is sized to fit within a bone tunnel so that a graft member may be accommodated between a wall of a bone tunnel and an outer surface of the radially expandable sheath. A sheath expander is disposable in a central lumen of the radially expandable sheath to radially expand the sheath so as to fix the graft member within the bone tunnel. The structurally weakened fracture region is adapted to fracture upon radial expansion of the sheath to allow varying amounts of radial expansion.
In specific embodiments of this aspect of the invention, a number of longitudinal side wall segments can be provided, the segments being connected by longitudinal fracture regions. The side wall segments can also have concave outer surfaces so that each segment can capture a portion of graft material between its outer surface and the bone tunnel wall. In a further embodiment, the segments can be longitudinally divided into subsegments connected by longitudinal flexion regions.
In another aspect of the invention, a graft fixation device for fixing a graft member within a bone tunnel includes a radially expandable sheath having a side wall comprising a plurality of longitudinal side wall segments separated by convex longitudinal flex regions having convex outer surfaces, the radially expandable sheath being sized to fit within a bone tunnel and defining a central lumen. In this aspect, the side wall segments are flexible and have a concave outer surface adapted to enclose a graft member between the concave outer surface and a bone tunnel wall. A sheath expander is disposable in the central lumen of the radially expandable sheath to flex the convex longitudinal flex regions and the flexible concave wall segments to radially expand the sheath so as to fix a graft member within a bone tunnel.
In specific embodiments of this aspect, the side wall segments may include rigid longitudinal subsegments connected by longitudinal flex regions to provide flexing within the segments. In addition, convex longitudinal flex regions may be configured to flex, but then fracture to allow further radial expansion of the sheath.
Graft fixation devices of the invention allow a wider variety of materials to be used to form the radially expanding sheath and can also allow a single sized sheath to be used with a larger variety of bone tunnel and expander sizes.